1. Field of the Invention
This invention relates to laundry detergent compositions containing a soil release polymer, and, more particularly, to a standard detergent formulation containing a homopolymer of vinyl caprolactam having a K-value of at least 40, preferably 40-50, which have particularly effective soil release and fabric softening properties.
2. Description of the Prior Art
Non-ionic surfactants are useful in removing oily stains from fabrics. Moreover, the presence of a soil release polymer enhances the removal of these stains by providing a sacrificial barrier to the fabric, which is removed during wash. There are quite a few soil release polymers currently available for use in powdered detergents. However, most of these polymers work only on synthetic fibers and on blends but not on cotton. The ability of these polymers to function as effective soil release agents depends on the hydrophobic-hydrophilic balance of the polymer; in particular, it is the hydrophobic segment of the polymer which adsorbs onto the hydrophobic polyester surface leaving the hydrophilic component free to render the surface hydrophilic.
R. Ruppert et al, in U.S. Pat. Nos. 4,579,681 and 4,614,519, described laundry detergent compositions which included various vinyl caprolactam copolymers, and vinyl caprolactam homopolymer. The disclosed vinyl caprolactam copolymers (Exs. 1-4) and homopolymer (Ex. 5), were considered useful over a wide number average molecular weight range, extending from 1,000 to 1,000,000. In fact, the process for making the vinyl caprolactam homopolymer of Example 5 produced a homopolymer having a K-value of only 36. No other caprolactam homopolymers were prepared or tested by Ruppert.
Other laundry detergent compositions containing soil release polymers are described in U.S. Pat. Nos. 5,866,525; 5,789,365; 5,733,856; and 4,968,451; and WO95/07336.
Accordingly, it is an object of this invention to provide laundry detergent compositions including a vinyl caprolactam homopolymer of defined K-value which provides particularly effective soil releasing and fabric softening properties as compared to the homopolymer and copolymers of the prior art.